An unbidden guest must bring his own stool with him.

Understand the thought

Meaning in plain English

Someone who arrives without an invitation should not assume that everything has been prepared for them. Bringing a stool pictures taking responsibility for the practical consequences of joining unexpectedly, rather than demanding extra hospitality.

What the words are saying

An unbidden guest is someone who has not been invited. The stool is a small but necessary provision: an unexpected arrival cannot assume that a place is already waiting. The image draws attention to preparation, consent and the work an extra person can create for a host. Applied beyond a household visit, it may suggest asking before joining and contributing what is needed if participation is welcome. It does not make arriving with equipment a substitute for permission, nor does it require a host to admit someone who was not invited. Hospitality and personal boundaries can both matter without making either person responsible for every unforeseen need.

Everyday example

A neighbour asks whether there is room at a shared garden picnic and, after being welcomed, offers to bring a folding chair and an extra dish.

When to use it

Use it when discussing considerate preparation for an unexpected addition to a gathering or activity.

Agent-assisted editorial interpretation. This explains the words; it does not by itself verify their author or earliest origin.